Optimization of nested SQL queries revisited
SIGMOD '87 Proceedings of the 1987 ACM SIGMOD international conference on Management of data
Query graphs, implementing trees, and freely-reorderable outerjoins
SIGMOD '90 Proceedings of the 1990 ACM SIGMOD international conference on Management of data
Extensible/rule based query rewrite optimization in Starburst
SIGMOD '92 Proceedings of the 1992 ACM SIGMOD international conference on Management of data
Algebraic optimization of outerjoin queries
Algebraic optimization of outerjoin queries
SIGMOD '94 Proceedings of the 1994 ACM SIGMOD international conference on Management of data
Hypergraph based reorderings of outer join queries with complex predicates
SIGMOD '95 Proceedings of the 1995 ACM SIGMOD international conference on Management of data
Access path selection in a relational database management system
SIGMOD '79 Proceedings of the 1979 ACM SIGMOD international conference on Management of data
How to Extend a Conventional Optimizer to Handle One- and Two-Sided Outerjoin
Proceedings of the Eighth International Conference on Data Engineering
Efficient Processing of Outer Joins and Aggregate Functions
ICDE '96 Proceedings of the Twelfth International Conference on Data Engineering
Improved Unnesting Algorithms for Join Aggregate SQL Queries
VLDB '92 Proceedings of the 18th International Conference on Very Large Data Bases
CASCON '95 Proceedings of the 1995 conference of the Centre for Advanced Studies on Collaborative research
No regression algorithm for the enumeration of projections in SQL queries with joins and outer joins
CASCON '95 Proceedings of the 1995 conference of the Centre for Advanced Studies on Collaborative research
Adding subqueries to MySQL, what does it take to have a decision-support engine?
Proceedings of the 5th ACM international workshop on Data Warehousing and OLAP
View matching for outer-join views
VLDB '05 Proceedings of the 31st international conference on Very large data bases
View matching for outer-join views
The VLDB Journal — The International Journal on Very Large Data Bases
Exploiting maximal redundancy to optimize SQL queries
Knowledge and Information Systems
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The strength of commercial query optimizers like DB2 comes from their ability to select an optimal order by generating all equivalent reorderings of binary operators. However, there are no known methods to generate all equivalent reorderings for a SQL query containing joins, outer joins, and groupby aggregations. Consequently, some of the reorderings with significantly lower cost may be missed. Using hypergraph model and a set of novel identities, we propose a method to reorder a SQL query containing joins, outer joins, and groupby aggregations. While these operators are sufficient to capture the SQL semantics, it is during their reordering that we identify a powerful primitive needed for a dbms. We report our findings of a simple, yet fundamental operator, generalized selection, and demonstrate its power to solve the problem of reordering of SQL queries containing joins, outer joins, and groupby aggregations.